In a communication system such as WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), or LTE-A (LTE-Advanced) established by the 3GPP (Third Generation Partnership Project) or wireless LAN or WiMAX (Worldwide Interoperability for Microwave Access) established by the IEEE (Institute of Electrical and Electronics Engineers), a base station apparatus (a cell, a transmission station, a transmission device, or an eNodeB) and a terminal apparatus (a mobile terminal apparatus, a reception station, a mobile station, a reception device, or UE (user equipment)) each include a plurality of transmission and reception antennas, and use a MIMO (multi-input, multi-output) technique in order to spatially multiplex data signals and realize high-speed data communication.
In order to realize data communication between the base station apparatus and the terminal apparatus in such a communication system, the base station apparatus needs to perform various types of control on the terminal apparatus. Therefore, the base station apparatus performs downlink and uplink data communication with the terminal apparatus by transmitting control information using certain resources. For example, the base station apparatus realizes data communication by transmitting resource assignment information, data signal modulation and coding information, data signal spatial multiplex number information, transmission power control information, and the like to the terminal apparatus. For such control information, a method described in NPL 1 may be used.
In addition, one of various methods may be used as a downlink communication method in which the MIMO technique is used, that is, for example, a multi-user MIMO scheme in which the same resources are assigned to different terminal apparatuses, a CoMP (cooperative multipoint or coordinate multipoint) scheme in which a plurality of base station apparatuses perform data communication in cooperation with one another, or the like may be used.
FIG. 35 is a diagram illustrating an example in which the multi-user MIMO scheme is implemented. In FIG. 35, a base station apparatus 3501 performs data communication with a terminal apparatus 3502 through a downlink 3504 and performs data communication with a terminal apparatus 3503 through a downlink 3505. At this time, the terminal apparatus 3502 and the terminal apparatus 3503 perform data communication in which multi-user MIMO is used. In the downlink 3404 and the downlink 3505, the same resources are used. The resources are configured by resources in a frequency domain and a time domain. In addition, the base station apparatus 3501 uses a precoding technique or the like to control beams for the downlink 3504 and the downlink 3505, thereby maintaining orthogonality between the downlink 3504 and the downlink 3505 and reducing cochannel interference. As a result, the base station apparatus 3501 can realize data communication that uses the same resources for the terminal apparatus 3502 and the terminal apparatus 3503.
FIG. 36 is a diagram illustrating an example in which a downlink CoMP scheme is implemented. In FIG. 36, a case is illustrated in which a radio communication system that uses a heterogeneous network configuration is constructed by a macro base station apparatus 3601 having wide coverage and an RRH (remote radio head) 3602 having narrower coverage than the macro base station apparatus 3601. Here, assume a case in which the coverage of the macro base station apparatus 3601 includes part or the entirety of the coverage of the RRH 3602. In the example illustrated in FIG. 36, the heterogeneous network configuration is constructed by the macro base station apparatus 3601 and the RRH 3602, which perform data communication with a terminal apparatus 3604 through a downlink 3605 and a downlink 3606, respectively, in cooperation with each other. The macro base station apparatus 3601 is connected to the RRH 3602 through a line 3603, and can transmit and receive control signals and data signals to and from the RRH 3602. As the line 3603, a wired line such as an optical fiber or a wireless line that uses a relay technology may be used. At this time, the macro base station apparatus 3601 and the RRH 3602 use similar or exactly the same frequencies (resources) in order to improve total spectral efficiency (transmission capacity) in the area of the coverage constructed by the macro base station apparatus 3601.
When the terminal apparatus 3604 is located close to the base station apparatus 3601 or the RRH 3602, the terminal apparatus 3604 can perform single-cell communication with the base station apparatus 3601 or the RRH 3602. Furthermore, when the terminal apparatus 3604 is located close to an edge (cell edge) of the coverage constructed by the RRH 3602, measures against cochannel interference from the macro base station apparatus 3601 need to be taken. Methods for reducing or suppressing interference with the terminal apparatus 3604 in a cell edge region by using a CoMP scheme in which the macro base station apparatus 3601 and the RRH 3602 cooperate in multi-cell communication (coordinated communication, multipoint communication, or CoMP) of the macro base station apparatus 3601 and the RRH 3602 have been examined. For example, as such a CoMP scheme, a method described in NPL 2 has been examined.
FIG. 37 is a diagram illustrating an example in which an uplink CoMP scheme is implemented. In FIG. 37, a case is illustrated in which a radio communication system that uses a heterogeneous network configuration is constructed by a macro base station apparatus 3701 having wide coverage and an RRH (remote radio head) 3702 having narrower coverage than the macro base station apparatus 3701. Here, assume a case in which the coverage of the macro base station apparatus 3701 includes part or the entirety of the coverage of the RRH 3702. In the example illustrated in FIG. 37, the heterogeneous network configuration is constructed by the macro base station apparatus 3701 and the RRH 3702, which perform data communication with a terminal apparatus 3704 through an uplink 3705 and an uplink 3706, respectively, in cooperation with each other. The macro base station apparatus 3701 is connected to the RRH 3702 through a line 3703, and can transmit and receive reception signals, control signals, and data signals to and from the RRH 3702. As the line 3703, a wired line such as an optical fiber or a wireless line that uses a relay technology may be used. At this time, the macro base station apparatus 3701 and the RRH 3702 use similar or exactly the same frequencies (resources) in order to improve total spectral efficiency (transmission capacity) in the area of the coverage constructed by the macro base station apparatus 3701.
When the terminal apparatus 3704 is located close to the base station apparatus 3701 or the RRH 3702, the terminal apparatus 3704 can perform single-cell communication with the base station apparatus 3701 or the RRH 3702. In this case, when the terminal apparatus 3704 is located close to the base station apparatus 3701, the base station apparatus 3701 receives and demodulates a signal received through the uplink 3705. On the other hand, when the terminal apparatus 3704 is located close to the RRH 3702, the RRH 3702 receives and demodulates a signal received through the uplink 3706. Furthermore, when the terminal apparatus 3704 is located close to an edge (cell edge) of the coverage constructed by the RRH 3702 or an intermediate point between the base station apparatus 3701 and the RRH 3702, the macro base station apparatus 3701 receives a signal received through the uplink 3705 and the RRH 3702 receives a signal received through the uplink 3706. Thereafter, the macro base station apparatus 3701 and the RRH 3702 transmit and receive, through the line 3703, the signals received from the terminal apparatus 3704, combine the signals received from the terminal apparatus 3704, and demodulate the combined signals. As a result of this processing, improvement of the performance of the data communication is expected. This is a method called joint reception. By using a CoMP scheme in which the macro base station apparatus 3701 and the RRH 3702 cooperate in uplink multi-cell communication (also referred to as coordinated communication, multipoint communication, or CoMP), the performance of the data communication in a cell edge region or a region around an intermediate point between the macro base station apparatus 3701 and the RRH 3702 can be improved.